Non alcoholic fatty liver disease (NAFLD) is a major health problem in the United States. It is seen in nonobese and obese patients and accompanied by complications of insulin resistance, type 2 diabetes and cardiovascular disease. Exacerbation of the inflammatory response has been shown to be essential for progression of NAFLD into steatosis, cirrhosis and even hepatocellular carcinoma. Immunoregulation and inflammation are controlled by infiltrating myeloid cells and resident macrophages (Kupffer cells), which regulate activation status of T- cells, NKT cells, NK cells and hepatocytes, all of which are critical for the development of NAFLD. However, the mechanisms that link inflammation to development of NAFLD are poorly understood. Therefore, it is important to identify novel factors and pathways that control the intensity and the duration f the inflammatory response in the liver. Screening for novel regulators of inflammation, we identified disabled homolog 2 (Dab2) as being downregulated in pro-inflammatory M1 and upregulated in anti-inflammatory M2 macrophages. Dab2 is a putative mitogen-responsive phosphoprotein, whose expression is downregulated in various forms of cancer, indicating its role as tumor suppressor. We found that Dab2 binds to components of the NF-kappaB signalling pathway and deletion of Dab2 in myeloid cells in mice resulted in protection of the liver against endotoxemia and high fat diet- induced steatosis. We will test the central hypothesis that myeloid Dab2 is essential for the progression of inflammatory hepatic tissue damage and NAFLD. In a multidisciplinary approach, we will use molecular and cell biological, as well as state of the art immunological methods, lipidomics, and conditional knock out mouse models of endotoxin- and diet- induced liver disease. Specific Aim 1 will test the hypothesis that Dab2 in myeloid-derived cells controls liver inflammation and NAFLD. Specific Aim 2 will determine the mechanistic basis for Dab2-dependent regulation of inflammation and Specific Aim 3 will examine the hypothesis that Dab2 in myeloid cells is essential for cross talk with NK cells in the liver.